Experimental Physics and
Industrial Control System

Hi Andrew,
> How heavily loaded are the callback threads cb{Low,Medium,High}?
The two cbLow threads use 5-10% CPU each. Load on the cb{Medium,High}
threads is 0.0%.
> Do you have chains of records that are linked together?
Only a small fraction of the input records are linking to calc records
or similar. No long chains of records or output records that could take
long to process.

> What other resources do your devices share that might limit how fast
> the IOC can communicate with them?
Hmm, I can't think of anything other than RAM (of which we have more
than enough - 24 GB) and the network interface (according to the
hypervisor's monitoring we are using only a small percentage of it's
bandwidth).

> How long does it take to "talk" to each device?
I'll measure the latency tomorrow.

> Multiple callback threads was certainly added, and I suspect it
> might help your situation because the second-half asynchronous
> processing is probably happening there.
I think you're right about this. I actually had to bump up the resources
a little to prevent cbLow queue overflows:

scanOnceSetQueueSize(10000)
callbackSetQueueSize(10000)
callbackParallelThreads(2, "Low")

Queue status after the IOC is running for a while:

epics> callbackQueueStatus
PRIORITY  HIGH-WATER MARK  ITEMS IN Q  Q SIZE  % USED  Q OVERFLOWS
   cbLow             3186           0   10000     0.0            0
cbMedium                0           0   10000     0.0            0
  cbHigh                0           0   10000     0.0            0
epics> scanOnceQueueStatus
PRIORITY  HIGH-WATER MARK  ITEMS IN Q  Q SIZE  % USED  Q OVERFLOWS
scanOnce              630           0   10000     0.0            0

Thanks,

Martin

-- 
Martin Konrad
Facility for Rare Isotope Beams
Michigan State University
640 South Shaw Lane
East Lansing, MI 48824-1321, USA
Tel. 517-908-7253
Email: [email protected]

References:

Excessive scan times for periodic scans Konrad, Martin via Core-talk

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